kripton@ayanta ~ $ qtdemo
X Error: BadMatch (invalid parameter attributes) 8
  Major opcode: 1 (X_CreateWindow)
  Resource id:  0x156
X Error: BadWindow (invalid Window parameter) 3
  Major opcode: 3 (X_GetWindowAttributes)
  Resource id:  0x5800004
Segmentation fault
kripton@ayanta ~ $ gdb qtdemo
GNU gdb (Gentoo 7.4 p1) 7.4
Copyright (C) 2012 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-pc-linux-gnu".
For bug reporting instructions, please see:
<http://bugs.gentoo.org/>...
Reading symbols from /usr/bin/qtdemo...(no debugging symbols found)...done.
(gdb) run
Starting program: /usr/bin/qtdemo 
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
[New Thread 0x7fffe7911700 (LWP 28699)]
[Thread 0x7fffe7911700 (LWP 28699) exited]                                                                                                                                                                           
[New Thread 0x7fffe7911700 (LWP 28700)]                                                                                                                                                                              
X Error: BadMatch (invalid parameter attributes) 8                                                                                                                                                                   
  Major opcode: 1 (X_CreateWindow)                                                                                                                                                                                   
  Resource id:  0x156                                                                                                                                                                                                
X Error: BadWindow (invalid Window parameter) 3                                                                                                                                                                      
  Major opcode: 3 (X_GetWindowAttributes)                                                                                                                                                                            
  Resource id:  0x5800004                                                                                                                                                                                            
                                                                                                                                                                                                                     
Program received signal SIGSEGV, Segmentation fault.                                                                                                                                                                 
0x00007ffff35c6240 in XVisualIDFromVisual () from /usr/lib64/libX11.so.6                                                                                                                                             
(gdb) bt                                                                                                                                                                                                             
#0  0x00007ffff35c6240 in XVisualIDFromVisual () from /usr/lib64/libX11.so.6                                                                                                                                         
#1  0x00007ffff65b124e in ?? () from /usr/lib64/qt4/libQtGui.so.4                                                                                                                                                    
#2  0x00007ffff65b12f0 in ?? () from /usr/lib64/qt4/libQtGui.so.4                                                                                                                                                    
#3  0x00007ffff65b417c in QWidgetPrivate::create_sys(unsigned long, bool, bool) () from /usr/lib64/qt4/libQtGui.so.4                                                                                                 
#4  0x00007ffff6564ded in QWidget::create(unsigned long, bool, bool) () from /usr/lib64/qt4/libQtGui.so.4                                                                                                            
#5  0x00007ffff6b9c29e in QEgl::createSurface(QPaintDevice*, void*, QEglProperties const*) () from /usr/lib64/qt4/libQtGui.so.4                                                                                      
#6  0x00007ffff70eb018 in QGLContext::chooseContext(QGLContext const*) () from /usr/lib64/qt4/libQtOpenGL.so.4                                                                                                       
#7  0x00007ffff7075f2f in QGLContext::create(QGLContext const*) () from /usr/lib64/qt4/libQtOpenGL.so.4                                                                                                              
#8  0x00007ffff70e9d25 in QGLWidget::setContext(QGLContext*, QGLContext const*, bool) () from /usr/lib64/qt4/libQtOpenGL.so.4                                                                                        
#9  0x00007ffff707626c in ?? () from /usr/lib64/qt4/libQtOpenGL.so.4                                                                                                                                                 
#10 0x00007ffff70e9dd2 in ?? () from /usr/lib64/qt4/libQtOpenGL.so.4                                                                                                                                                 
#11 0x00007ffff707707e in QGLWidget::QGLWidget(QWidget*, QGLWidget const*, QFlags<Qt::WindowType>) () from /usr/lib64/qt4/libQtOpenGL.so.4                                                                           
#12 0x000000000042d0bb in ?? ()                                                                                                                                                                                      
#13 0x000000000042e1bf in ?? ()                                                                                                                                                                                      
#14 0x000000000040eb62 in ?? ()                                                                                                                                                                                      
#15 0x00007ffff534a22c in __libc_start_main () from /lib64/libc.so.6                                                                                                                                                 
#16 0x000000000040ea29 in ?? ()                                                                                                                                                                                      
#17 0x00007fffffffd8a8 in ?? ()                                                                                                                                                                                      
#18 0x000000000000001c in ?? ()                                                                                                                                                                                      
#19 0x0000000000000001 in ?? ()                                                                                                                                                                                      
#20 0x00007fffffffdcb9 in ?? ()                                                                                                                                                                                      
#21 0x0000000000000000 in ?? ()                                                                                                                                                                                      
(gdb) x                                                                                                                                                                                                              
Argument required (starting display address).                                                                                                                                                                        
(gdb) q                                                                                                                                                                                                              
A debugging session is active.                                                                                                                                                                                       

        Inferior 1 [process 28676] will be killed.

Quit anyway? (y or n) y